1. Field of the Invention
The present invention relates to a food storage container for fermenting and/or storing foodstuffs at a preset temperature and, more particularly, to a temperature sensing device for such a food storage container, which is arranged outside the interior of the food storage container and is mechanically coupled to the exterior side of an inner liner as well as to at least a portion of the piping of an evaporator, such that an efficient thermal conduction is established therewith.
2. Discussion of the Related Art
Fermented foodstuffs such as kimchi and yogurt require an accurately controlled process in order to attain an optimum or particular taste, so that a given foodstuff is fermented (ripened) at a specific high temperature for an appropriate period of time. In order to preserve the fermented result and to retain the particular taste for a long period of time, the foodstuff is then stored under refrigerated conditions, immediately following the fermentation step, in a food storage container brought to and maintained at a carefully selected and precisely controlled low temperature. In order to carry out this process, the food storage container is equipped with internally integrated systems for containing a foodstuff to be processed.
In the operation of a food storage container as described above, the heating system operates according to a user selection of a desired degree of ripeness, which selectively ferments the foodstuff loaded therein, by maintaining the interior chamber at an appropriate temperature. Upon completion of the fermentation step, a refrigeration cycle is initiated and the cooling system operates to decrease the chamber's internal temperature and thereafter maintain (store) the foodstuff at an appropriate temperature. Throughout this process, the operation of the food storage container must be accurately controlled, especially in terms of the set temperature of the interior chamber. To this end, it is most important to accurately sense the chamber's internal temperature. An accurate sensing of this temperature, however, is very difficult due to several factors, such as the prevailing deviation in the temperature distribution exists in the chamber's interior during the operation of the food storage container, especially when driving the cooling system. Also, a convection phenomenon occurring between warm air and cold air results in generally lower temperatures concentrated in a lower chamber area and generally higher temperatures concentrated in an upper chamber area.
Though some of these difficulties in accurate temperature detection are present in any ordinary refrigerator, some are particularly acute in food storage containers such as that described above. For example, the normal operation begins with a foodstuff at approximately room temperature, which is then heated to a high temperature to allow for fermentation, after which time the heated result is immediately cooled to a low temperature. In such cases, the temperature differential which exists between the foodstuff itself and the ambient chamber temperature is apt to be more extreme than in an ordinary refrigeration process. Moreover, another heating cycle may begin following a previous cooling cycle, that is, while the chamber temperature is still very cold. Overall, depending on these interior conditions, there is the tendency for inconsistent reactions to cooling (or heating) efforts, such as the sudden turning on and off of the cooling system and the associate application of coolant within an evaporator, or the mere opening and closing of the internal chamber during operation. Yet, as stated above, the obtained taste of the kimchi or yogurt produced relies heavily on the accuracy of the entire process.
Typically, a food storage container, e.g., a refrigerator, a temperature sensor is disposed in the interior of the chamber and thereby serves to detect the internal temperature of the chamber in order to control the load operation of the food storage container based on the detected temperature. By arranging the temperature sensor in the interior of the chamber, however, the internally detected temperature is insufficient for load control operations. That is, due to the above described difficulties in temperature detection, the internal chamber exhibits undesired fluctuations in temperature as a compressor of the cooling system is controlled, i.e., turned on and off, based on the temperature detected conventionally. As a result of these deficiencies, the foodstuff being stored in the chamber cannot be preserved at an optimum state for a long period of time.
For example, when the detected temperature rises about 2.about.4.degree. C. above a desired storage temperature of, say, 0.degree. C., the compressor turns on, with the aim to decrease the detected temperature until reaching the set storage temperature. In this case, the temperature sensed by the internally situated temperature sensor corresponds to a local temperature at one portion of the storage chamber, namely, in the immediately adjacent area of the temperature sensor. On the other hand, where the operation of the food storage container is for fermentation, the internal temperature of the storage chamber is increased using a heater which is controlled to maintain a temperature range of, say, 18.about.24.degree. C., turning on when the chamber temperature drops below 18.degree. C. and turning off when the chamber temperature rises above 24.degree. C. In practice, however, a variation in the internal temperature of the storage chamber proceeds slowly by virtue of an inefficient thermal conduction occurring in the chamber through the foodstuff, namely, kimchi, contained therein. As a result, a considerable temperature deviation exists within the storage chamber during the cooling/heating (load) operation, which greatly impedes efforts to ripen and preserve the stored foodstuff at a desired state. Due to the convection phenomenon and the resulting temperature differential between upper and lower portions of the storage chamber, excessive cooling may occur if the food storage container is controlled based on the temperature sensed at the upper portion, and excessive heating may occur if the food storage container is controlled based on the temperature sensed at the lower portion. The occurrence of any one of the aforementioned problems of the conventional art results in a deterioration in the state (taste) of the stored foodstuff, and particulary, the preservation period is reduced.
To partially combat these problems, the food storage container may be additionally provided with an acidity sensor in the case of a kimchi refrigerator. The acidity sensor can detect the degree of ripeness of kimchi stored in a kimchi storage chamber, which enables more accurate control, but the problem resulting from a temperature deviation occurring within the storage chamber remains and the preservation period is reduced accordingly. Such a reduction in food preservation period may be overcome by installing a plurality of temperature sensors to be distributed throughout the interior of the storage chamber, to take into consideration its uneven temperature distribution. This approach, however, increases production costs and contributes to the complexity of the entire system.